1. Field of the Invention
This invention relates to an inscribed meshing planetary gear construction which is preferably applied to a speed increasing gear or a reduction gear, more particularly, a small-sized speed increasing gear or a reduction gear in which a high output torque is required.
2. Description of the Prior Art
In the prior art, it is widely known to provide a speed increasing gear or a reduction gear employing an inscribed meshing planetary gear construction comprising a first shaft, an external-tooth gear mounted (assembled) on the first shaft through a eccentric body in a state where the external-tooth gear can be rotated eccentric around the first shaft, an internal-tooth gear with which the external-tooth gear is inscribed and meshed, and a second shaft connected to the external-tooth gear through means for transmitting only the rotation component of the external-tooth gear.
An example of the prior art of this construction is shown in FIGS. 14 and 15. This prior art is constructed such that said first shaft is applied as an input shaft, said second shaft is applied as an output shaft and at the same time said construction is applied to a reduction gear by fixing the internal-tooth gear.
Eccentric bodies 3a, 3b are fitted to the input shaft 1 with a predetermined phase difference (180.degree. in this example). The eccentric bodies 3a, 3b are integrated into one body. Two external-tooth gears 5a, 5b are placed on to each of these eccentric bodies 3a, 3b through eccentric bearings 4a, 4b. A plurality of inner roller holes 6 are provided in the external-tooth gears 5a, 5b and then an inner pin 7 and an inner roller 8 are fitted in these roller holes.
A main object of providing two external-tooth gears (in plural rows) is to increase a transmittance capacity, maintain a strength and keep a rotational balance.
External teeth 9 such as trochoidal teeth or circular teeth etc. are provided at outer circumferences of said external-tooth gears 5a, 5b. The outer teeth 9 are inscribed and meshed with the internal-tooth gear 10 fixed to a casing 12. The internal teeth of the internal-tooth gear 10 are constructed such that an outer pin 11 is loosely fitted to an inner pin hole 13 and held to be easily rotatable.
An inner pin 7 passing through said external-tooth gears 5a, 5b is tightly fitted to or fixed to a flange part 14 of the output shaft 2.
When the input shaft 1 is rotated once, the eccentric bodies 3a, 3b is also rotated once. The external-tooth gears 5a, 5b are apt to oscillatebly rotate around the input shaft 1 through this one revolution of the eccentric bodies 3a and 3b. However, since the rotation is restricted by the internal-tooth gear 10, the external-tooth gears 5a, 5b almost merely perform oscillation while being inscribed with the internal-tooth gear 10.
Now, it is assumed that the number of teeth of the external-tooth gears 5a, 5b is N and the number of teeth of the internal-tooth gear 10 is N+1, then the difference between the numbers of teeth is 1. Consequently, the external-tooth gears 5a, 5b are displaced by one tooth relative to the internal-tooth gear 10 fixed to the casing 12 every time the input shaft 1 is rotated. This means that one revolution of the input shaft 1 is decelerated to a revolution of -1/N of the internal-tooth gear.
Oscillation component of the external-tooth gears 5a, 5b is absorbed by clearances between the inner roller holes 6 and the inner pins 7 and then only the rotational component is transmitted to the output shaft 2 through the inner pins 7.
In this case, the inner roller holes 6a, 6b and the inner pins 7 (inner rollers 8) form an "isokinetic inscribed meshing mechanism".
As a result, finally, a reduction of reduction ratio -1/N can be accomplished.
In the example of this prior art, the internal-tooth gear of the inscribed meshing planetary gear construction is fixed, the first shaft is an input shaft and the second shaft is an output shaft. However, a reduction gear can also be constructed by fixing the second shaft and applying the first shaft as an input shaft and the internal-tooth gear as an output shaft. Furthermore, a speed increasing gear can also be constructed by reversing these inputs and outputs.
As described above, the inner pin 7 has a function to form an circular tooth acting as one of elements of said isokinetic inscribed meshing mechanism constructed with the inner roller holes 6a, 6b, and also has another function acting as a carrier member for transmitting a rotational force of a rotation of external-tooth gears 5a, 5b to the output shaft 2. In particular, in order to keep a superior former function, it was essential to provide the inner rollers 8 capable of being freely rotated around the outer circumference of the inner pins 7. The inner roller 8 shows a problem of expensive cost due to the fact that the material must be hard and both outer and inner circumferences thereof must be coaxially and accurately machined (processed or manufactured).
In view of this fact, an idea has been proposed that the function which forms a circular tooth of one of the elements of the isokinetic inscribed meshing mechanism and another function which acts as a carrier member for transmitting a rotational force of the external-tooth gears 5a, 5b to the output shaft 2 are separated, and even if the inner roller 8 is eliminated, it has a similar performance to that of having the inner roller 8.
This structure is illustrated in FIGS. 17 and 18.
This structure comprises, as means for transmitting a rotational component of the external-tooth gears, the inner pin 7 capable of constructing the isokinetic inscribed meshing mechanism relative to the inner pin holes (corresponding to the inner roller holes) 19a, 19b arranged in the external-tooth gears 5a, 5b, an annular support ring 17 receiving a rotation corresponding to the rotational component of the inner pin 7 (=the rotational component of the external-tooth gears), and a carrier pin 16 projected from the flange part 14 formed at the output shaft 2, connected and fixed to the support ring 17.
Said inner pin 7 is rotatably fitted to the flange part 14 and the support ring 17 through bushes 18a, 18b. That is, since the inner pin 7 is not necessarily tightly connected to the output shaft 2 due to the presence of the carrier pin 16, it can be constructed to be rotatable, resulting in that the prior art inner roller 8 can be eliminated: Said annular support ring 17 is assembled to an extremity end portion of said carrier pin 16. Since the carrier pin 16 only has a function to transmit a rotational force of the support ring 17 to the output shaft, there are provided big through-holes 20a, 20b which do not interfere with the carrier pin 16 even if the carrier pin 16 oscillates at the corresponding portion on the external-tooth gears 5a, 5b.
Incidentally, in FIG. 17, reference numerals 15a, 15b denote bearings of the output shaft 2. Reference numeral 21 denotes an inner pin keep plate for determining an axial position of the inner pin 7. Reference numeral 23 denotes an inner pin keep bolt. Reference numeral 22 denotes a steel plate race.
Although the prior art illustrated in FIGS. 14, 15 and FIGS. 17, 18 is "an inscribed meshing planetary gear construction" having two external-tooth gears, it is apparent that more simple type having one external-tooth gear may also be presented. This example is illustrated in FIGS. 19 and 20. However, as the inscribed meshing planetary gear construction, it is quite similar to those illustrated in FIGS. 14, 15 and FIGS. 17, 18, so that similar locations are merely denoted by reference symbols having no suffixes a and b and their duplicate description will be eliminated.
By the way, it is normal that a speed increasing gear or reduction gear having the aforesaid inscribed meshing planetary gear construction has a transmitting capacity of about 0.1-160 KW. When a transmitting capacity is lower than the former, it is normal that a parallel axis type gear reduction gear having a normal involute gear teeth is applied. Because, in this case, a part of the reduction gear mechanism can be made compact as compared with a size of a motor without depending on the inscribed meshing planetary gear construction (an outer diameter of the part of the reduction gear mechanism can easily be the same diameter in respect to an outer diameter of the motor).
An example of a geared motor 40 is illustrated in FIGS. 22-24, which is integrally constructed with the motor using the well-known parallel axis gear reduction gear mechanism. FIG. 22 is a front elevational view, and FIG. 23 is a side elevational view as viewed from an installing surface 42. FIG. 24 is a sectional view showing a gear reduction gear mechanism part 44 as a developed section.
However, as apparent from FIGS. 14, 17 and 19, this prior art type reduction gear was constructed such that a variation of load generated at the reduction gear mechanism part or an external radial load from a mating mechanism acting against the output shaft 2 was supported by a pair of bearings 15a and 15b supporting output shaft 2, so that it is need in generally that a Y segment in each of the figures was elongated and an X segment was shortened as much as possible in order to increase a supporting stability.
However, there was a problem that the X segment was hardly shortened and the Y segment was necessarily elongated, resulting in that the axial length of the reduction gear was elongated.
In addition, in case of a structure shown in FIGS. 17 and 18, a carrier member 16 was integrally formed with the output shaft 2, resulting in that there was also a problem that the manufacturing was quite difficult, required a high cost and then an effect of cost reduction caused by elimination of inner rollers 8 was eliminated..
Furthermore, in order that the inner pins 7 were supported and free rotate, an inner pin pressing plate 21, a steel plate ring 22 and inner pin pressing bolts 23 and the like were essential, resulting in that there was also a problem that the number of component parts and the number of assembling steps were increased.
On the other hand, in case of the structure shown in FIG. 21 in which the reduction gear shown in FIGS. 19 and 20 was fixed at its flange, the aforesaid problem was present as it was, and at the same time, since it had a double-flange structure in the casing 12 in which a distance Z between an installing flange 36 for the mating machine and a flange 37 for fixing an internal-tooth gear was elongated due to a requirement of the elongated Y segment, resulting in that, for example, when this structure was made by aluminum die-cast, or aluminum casting, the mold was complicated, the manufacturing was difficult and expensive.
In addition, in this kind of prior art inscribed meshing planetary gear construction including the aforesaid prior example, a connection between the input shaft 1 and eccentric bodies 3 or 3a, 3b was carried out under a combination of a key 30 and key-ways 31 and 32 (refer to FIGS. 19 and 20), resulting in that there was a problem that the number of machining steps and the number of component parts were increased and the end mill machining was required, so that an efficiency of the manufacturing was poor and a mass productivity was low.
In addition, there was a problem that a concentration of stress could easily be generated at the key-ways 31 and 32. Due to this fact, there was a requirement that the diameter of the input shaft 1 be made large as much as possible. However, there was a substantial restriction on an expansion of an outer diameter of the eccentric body in order to realize a compact characteristic of a speed increasing gear or reduction gear in the diametrical direction, and further there was a limitation in increasing in a diameter of the input shaft due to a requirement of assuring a wall thickness of the key-way 32.
By the way, as a method for position setting in the circumferential direction (stopping of rotation) of substantial coaxial two members, it is known as a general well-known technology in which a part of an outer circumference of an inner member is cut in parallel with an axial direction to form a cut part having about a D-shaped cross section, and this cut part is utilized to set a position of circumferential direction between the inner member.
However, in the case where such a structure as above is employed as a circumferential position setting structure between the input shaft 1 and the eccentric bodies 3, 3a and 3b of this kind of inscribed meshing planetary gear construction, a bearing 35 (in general, a ball bearing is utilized in view of a cost) at the output shaft must be necessarily a bearing of small diameter in which it inscribes against a flat surface of the cut part, it may not be allowed in view of its strength. As regards this matter, it may also be proposed that an inner diameter of the bearing 35 has the same diameter as that of the input shaft 1 and a filling material is enclosed at the cut part. However, this structure was not appropriate as a bearing structure for the input shaft 1 to which a force of radial direction was always applied due to an eccentric rotation of the external-tooth gear or bending of the output shaft.
That is, it was a practical situation in the prior art that this "method of cutting a part of an outer circumference of the input shaft in parallel with its axial direction" was hardly employed as a structure to be applied to this kind of inscribed meshing planetary gear construction.
The small sized geared motor using the parallel axis gears shown in FIGS. 22 and 24 was hardly used due to the fact that it could not get a high output torque and it was difficult in view of its structure that the motor (the input shaft 1) and the output shaft 2 were concentrically arranged as shown in FIG. 24.
There was a problem that a centering location and a fixing of the motor were hard due to the fact that the motor (the input shaft 1) and the output shaft 2 were not concentric and no fitting parts concentric with the output shaft 3 was prepared at the reduction gear mechanism.
The present first invention has been constructed in view of the aforesaid various problems of the prior art and it is an object of the present invention to provide an inscribed meshing planetary gear construction comprising;
the first shaft, an external-tooth gear placed on an eccentric axis on the first shaft through an eccentric body attached to the first shaft, an internal-tooth gear with which the external-tooth gear is inscribed and meshed, and the second shaft connected to the external-tooth gear through means for transmitting only a rotational (tangential) component of the external-tooth gear, wherein as means for said transmitting the rotational component, there are provided inner pins capable of forming an isokinetic inscribed meshing mechanism in respect to inner pin holes disposed in the external-tooth gear, an annular support ring for receiving a rotation corresponding to the rotational component of the external-tooth gear through the inner pins, and a carrier member projected from a flange part formed in the second shaft, connected and fixed to the support ring.
In the above construction, the annular support ring and the flange part of the second shaft are disposed while holding the external-tooth gear therebetween, and both the support ring and the flange part are supported at both ends to a casing through a pair of bearings. The carrier member is separated from the support ring and the flange part and formed in a substantial column-like shape. A pipe-like spacer is press fitted in advance at a center position of the carrier member. Both ends of the carrier member are press fitted to the support ring and the flange part. And axial position of the support ring, the carrier member and the flange part is set through the spacer.
Said inner pins may be freely fitted to the support ring and flange part.
Further, it is an object of the present second invention to overcome the aforesaid problem by arranging an inscribed meshing planetary gear construction comprising;
the first shaft, an external-tooth gear placed on an eccentric axis on the first shaft through an eccentric body attached to the first shaft, an internal-tooth gear with which the external-tooth gear is inscribed and meshed, and the second shaft connected to the external-tooth gear through means for said transmitting only a rotational component of the external-tooth gear, wherein as means for transmitting said rotational component, there are provided inner pins capable of forming an isokinetic inscribed meshing mechanism in respect to inner pin holes placed in the external-tooth gear, an annular support ring for receiving a rotation corresponding to the rotational component of the external-tooth gear through the inner pins, and a carrier member projected from a flange part formed in the second shaft, connected and fixed to the support ring.
In the above construction, the annular support ring and the flange part of the second shaft are attached while holding the external-tooth gear therebetween, and both the support ring and the flange part are supported at both ends to a casing through a pair of bearings. The carrier member is separated from the support ring and the flange part and formed in a substantial column-like shape. A pipe-like spacer is press fitted in advance at a center position of the carrier member. Both ends of the carrier member are freely fitted to the support ring and the flange part. Axial position of the support ring, carrier member and flange part is set by holding the flange part, spacer and support ring by means of a stopper ring means attached at one end of the carrier member and a screw-nut means attached at the other end of the carrier member.
Said inner pins may be loosely fitted to the support ring and flange part, their axial position is set by either the inner rings or outer rings of the pair of bearings.
It is an object of the present third invention to overcome the aforesaid problem by arranging an inscribed meshing planetary gear construction comprising; the first shaft, an external-tooth gear placed on an eccentric axis on the first shaft through an eccentric body attached to the first shaft, an internal-tooth gear with which the external-tooth gear is inscribed and meshed, and the second shaft connected to the external-tooth gear through means for transmitting only a rotational component of the external-tooth gear, wherein as means for said transmitting the rotational component, there are provided inner pins capable of forming an isokinetic inscribed meshing mechanism in respect to inner pin holes disposed in the external-tooth gear, an annular support ring for receiving a rotation corresponding to the rotational component of the external-tooth gear through the inner pins, and a carrier member projected from the flange part formed in a second shaft, connected and fixed to the support ring.
In the above construction, the annular support ring and the flange part of the second shaft are connected while holding the external-tooth gear therebetween, and both the support ring and the flange part are supported at both ends to a casing through a pair of bearings. A part of an outer circumference of the first shaft is cut in parallel with its axial direction to form a cut part having the cross sectional shape of about D-shape, and this cut part is utilized to define a positioning in the circumferential direction of each of the first shaft and the eccentric body.
In this case, an inner diameter of the bearing of the first shaft facing to the second shaft may be set to be slightly smaller than an outer diameter of the first shaft, and then a filling material is enclosed at a slight remained cut part.
It is an object of the present fourth invention to overcome the aforesaid problem by arranging an inscribed meshing planetary gear construction comprising a first shaft, an external-tooth gear placed on an eccentric axis on the first shaft through an eccentric body attached to the first shaft, an internal-tooth gear with which the external-tooth gear is inscribed and meshed, and a second shaft connected to the external-tooth gear through means for transmitting only a rotational component of the external-tooth gear, wherein as means for said transmitting the rotational component. There are provided inner pins capable of forming an isokinetic inscribed meshing mechanism in respect to inner pin holes disposed in the external-tooth gear, an annular support ring for receiving a rotation corresponding to the rotational component of the external-tooth gear through the inner pins, and a carrier member projected from a flange part formed on the second shaft, connected to and fixed to the support ring.
In the above construction,the annular support ring and the flange part of the second shaft are attached while holding the external-tooth gear therebetween, and both the support ring and the flange part are supported at both ends at a casing through a pair of bearings. A square-shaped installing flange and a circular part for centering location are formed in the second shaft side of the casing in concentric with the second shaft and in concentric with the first shaft. And installing bolt holes are placed near a top point of the square-shaped installing flange.
In the present first to fourth inventions, the carrier member is passed through the external-tooth gear and attached hold the external-tooth gear with the annular support ring and the flange part of the second shaft, and both the support ring and the flange part are supported at both ends at a casing through a pair of bearings. As a result, it is possible to remarkably improve rigidity and stability of a reduction gear mechanism.
In the present first invention, as a structure for connecting and position setting the flange part, carrier member and support ring, the carrier member is separated from the support ring and the flange part and substantially formed into a column shape, and at the same time, a pipe-like spacer is press fitted in advance at a center position of the carrier member, thereafter both ends are press fitted to the support ring and flange part, so that an axial position of the support ring, carrier member and flange part is set through the spacer.
As a result, it is not necessary to make an integral projection of the carrier member from the flange part as found in the prior art, and not necessary to manufacture a complex structural member ranging from the flange part to the carrier member, and thus a cost can be substantially reduced. In addition, since the carrier itself is a structure in which a pipe-like spacer is fitted into a simple column-like shape; resulting in that the manufacturing is quite easy, and at the same time the strength and accuracy may become superior.
That is, if the carrier member itself is formed to have a stage which is found in a coupling structure between the support ring and the carrier member as found in the prior art, the manufacturing is difficult and the accuracy is hardly attained. Furthermore, a stress may easily be concentrated at a part indicated by a reference symbol P1 in FIG. 16. In addition, in order to eliminate this problem, it is necessary to make a round R at the part of said P1, and in this case, it is necessary to make a chamfer corresponding to the side of the support ring. However, since it is necessary to make a chamfer at a part of a stage indicated by a reference symbol P2, only a range L1 can contribute to an axial position setting. Therefore, in order to keep this range L1 as long as possible, it is necessary to increase a large diameter D1 or to decrease a small diameter D2, resulting in that there is a problem that the weight is increased or the strength is decreased.
To the contrary, the present first and second inventions are constructed in such a manner that a pipe-like spacer is merely fitted to a column-like carrier member, so that a concentration of stress is hardly produced, an entire thickness of the pipe can be utilized to set an axial position, and further an entire length (an axial length) of many the pipes can be easily arranged. And then, axial positions of a plurality of carrier members can easily be set.
Constitution described in the present first invention aims at an application to a so-called maintenance free small-sized speed increasing gear or reduction gear under an assumption that it is not frequently decomposed after once assembled.
Accordingly, the carrier member, flange part and support ring are connected by the most simple press-fitting so as to realize a low cost.
In this case, the structure can be simplified by press fitting the inner pins also into the flange and the support ring, resulting in that a more low cost can be attained.
On the other hand, construction described in the present second invention aims at an maintenance or repairing through the decomposition. Accordingly, it has a structure in which the flange part, a spacer for the carrier member and the support ring are held and fixed by the stopper ring means and the screw-nut means. The reason why the stopper ring means is employed consists in the fact that a stress is concentrated at the stage part if the carrier member having a stage part is employed, and that the staged member can not be machined by a so-called coreless grinding plate. Therefore, the cost is expensive and a high accurate machining can not be carried out.
In this case, in view of the decomposition, if inner pins are freely fitted to the flange part and the support ring, and an axial position is set by a pair of bearings holding the flange part and the support ring, the structure can be simplified and the inner pins can be freely rotated.
In the present third invention, similar to the present first and second inventions, a carrier member passes through the external-tooth gear and is disposed so that the external-tooth gear is held by the annular support ring and the flange part of the second shaft, and further both the support ring and the flanger part are supported at both ends at a casing through a pair of bearings. As a result, rigidity of the reduction gear mechanism, in particular, rigidity and stability in respect of the radial direction can be improved.
Due to employment of this construction, it becomes possible to make an inner diameter of the bearing of the second shaft smaller, and a part of an outer circumference can be cut in parallel with an axial direction of the first shaft to enable D-shaped cut part.
By forming the same shape hole including the cut part in the eccentric body, a position setting in the circumferential direction (stopping of rotation) can be obtained.
Since the structure for preventing the rotation can be employed, the cut part line between the first shaft and the eccentric body are changed from an acute angle (prior art) to an obtuse angle (third invention) so that a concentration of stress hardly occurs. Also, since a key which restricts a minimum thickness of the eccentric body is not present, it becomes possible to increase a diameter of the first shaft and at the same time it becomes possible to decrease an outer diameter of the eccentric body. Therefore, the load capacity can be increased or a more small sized eccentric body can be used in response to the application.
In the prior art, since the machining of key-way in the first shaft had to be cut by an end mill whereby a machining efficiency was quite inferior and a mass productivity was poor. However, in the case where a D-shaped cut part is formed, after many input shafts are arranged, and then the cut part is formed by a broach machining whereby the machining efficiency can be remarkably improved and the mass productivity is further improved. As a result, a further cost-reduction can be attained.
Also, the number of component parts can be naturally decreased in correspondence with no presence of key, so that the number of assembling operations can be reduced.
Although there is no special problem even if an inner diameter of the bearing of the first shaft facing to the second shaft is completely smaller diameter than that of a flat surface of the cut part due to said both supporting structures, it may be slightly lower set than that of an outer diameter of the first shaft (to a degree in which the cut part is slightly remained) and a filling material may be filled in the cut part slightly remained.
With such an arrangement, it becomes possible to present a reduction in strength of the bearing at the second shaft from increasing.
As a filling material, either resin or solder or the like can be applied.
Lastly, in the fourth present inventions, similar to the present first to third inventions, basically employed an inscribed meshing planetary gear construction, not so-called parallel axis gear structure, and then the carrier member passes through the external-tooth gear so that the external-tooth gear is held by the annular support ring and the flange part of the second shaft, and both the support ring and the flange part are supported at both ends at a casing through a pair of bearings. As a result, rigidity of the reduction gear mechanism, in particular, rigidity and stability against a radial direction can be remarkably improved. In addition, the flange for fixing the internal-tooth gear and the flange for installing to the mating machine can be integrally formed whereby the machining can be easily attained, the low cost and reduction in the axial direction size can be realized.
Furthermore, in the present fourth invention, the casing facing to the second shaft is formed with a square-shaped installing flange part as means for fixing to the mating machine, and installing bolt holes are disposed near a top part of the square-shaped installing flange. As a result, due to the both ends supporting structure, double-flange structure can be avoided, and at the same time a structure of the casing at the second shaft can be made quite simple, and then a smaller size and a lower cost than the prior art can be realized.
In addition, since this installing flange part has a square shape, "a seat setting" as a simple reduction gear machine under a state before being fixed to the mating machine is superior, and it may not roll, resulting in that it has an advantage that it may easily be handled.
With such a construction described above, the present invention may provide a small-sized device, high output and further the first shaft and the second shaft (in general, the input shaft and the output shaft) can be concentrically made, resulting in that a centering and a fixing to the mating machine could easily be carried out under a presence of a fitting part formed in concentric with the second shaft.
In this way, according to the present invention (first to the fourth inventions), since the reduction gear mechanism is supported at both ends by a pair of bearings, and an entire length of the reduction gear machine can be shortened, and its structure is quite simple and it can be assembled with high accuracy while it has a construction comprising a support ring and a carrier member. In addition, an assembling structure of each of the inner pins is quite simple, so that entirely the high accuracy and a low cost can be obtain. As a result, a connecting structure between the first shaft and an eccentric body can be rationally improved, resulting in that entirely a high strength and a low cost can be obtained. In addition, employing this construction eliminates a double flange of the casing at the second shaft side so that the manufacturing of the casing at the output part can easily be performed in a low cost. In addition, although the first shaft, the second shaft, fitted part around the second shaft and installing bolt holes are concentrically arranged, so that centering and fixing of them to the mating machine can be quite easily be performed.